Screening apparatus

ABSTRACT

An apparatus for separating solids from liquids including an endless rotatably mounted band of collecting arms for collecting screened solid material, each of the collecting arms having a leading collecting face and two opposite sides adjacent the leading collecting face, and being mounted on support rods which are arranged in spaced relationship around the band, link pieces rigidly attached to the collecting arms for linking one support rod to the next, such that the link pieces form continuous chains around the band, and separate the collecting arms one from the other to form slots between the link pieces, said link pieces being rotatable on the support rods to which they are attached, and a rotatable set of discharging teeth arranged to cooperate with said movable band by entering the slots as the band rotates to move along the leading collecting faces of the collecting arms, thereby to remove collected material gathered at the slots and from said leading collecting faces of the collecting arms.

FIELD OF THE INVENTION

The present invention relates to a screening device for use in thetreatment of channelled water flows notably sewage, to remove detritussuch as rags, string, plastic bags, condoms, and rubbish of other than afinely divided nature which might interfere with subsequent treatmentprocesses.

BACKGROUND OF THE INVENTION

Difficulties are encountered in practice in the treatment ofcontaminated water flows such as sewage prior to fine filtration, due tothe presence of heavy and generally untreatable objects such as rags,string, plastic bags, and the like.

If such items are not removed then proper and adequate treatment of theliquid does not result, and blockage of ducts and channels may occur.

A screening device is known comprising a continuously movable endlessconveyor loop formed of a series of interconnected link pieces eachhaving a lifting hook on which material to be screened is collectedduring movement through the contaminated water flow, and a rearwardlyextending bar linkage.

The link pieces are mounted for rotatable movement on support rodsextending across the width of the band conveyor loop such that as thelink pieces are caused to rotate by means of a forced change indirection of travel of the loop, the books of the link pieces cooperatewith the bar linkages of other link pieces, such that the bar linkagesact to clear the hooks of collected material.

In addition a four armed rotating brush is used to clean the barlinkages of collected grease and similar unwanted deposits.

Whilst being effective, the prior art just described is complicated indesign and costly to manufacture. It also requires the presence of twoindependently operable mechanical means to maintain the operating partsclean and free from contamination matter which builds up over timethereby reducing overall efficiency.

SUMMARY OF THE INVENTION

It is the object of the present invention to obviate the deficiencies ofthe prior art.

According to the present invention there is provided a device forseparating solids from liquids comprising an endless rotatably mountedband of collecting arms for screened solid material, each of thecollecting arms having a leading collecting face and two opposite sidesadjacent the leading collecting face, and being mounted on support rodswhich are arranged in spaced relationship around the band, link piecesrigidly attached to the sides of collecting arms for linking one supportrod to the next, such that the link pieces form continuous chains aroundthe band, and separate the collecting arms one from the other to formslots between the link pieces, said link pieces being rotatable on thesupport rods to which they are attached, and a rotatable set ofdischarging teeth arranged to cooperate with said movable band byentering the slots as the band rotates to move along the leadingcollecting faces of the arms thereby to remove collected materialgathered at the slots and from said leading collecting faces of thecollecting arms.

Advantageously the discharging teeth are the teeth of a sprocket wheelwhich drives the movable band by means of said cooperation of the teeththereof with said slots and the collecting arms.

To avoid clogging and to ensure maximum discharge of collected materialat all times, scraper blades may be mounted between the continuouschains acting to dislodge matter accumulating on the flanks of thedischarging teeth and the surfaces of the link pieces.

Preferably, the leading collecting face of each collecting arm lies on acircle, the center of which is the axis of rotation on the support rodto which the link piece of each collecting arm is attached.

The discharging teeth of the sprocket wheel preferably taper to an edge,which edge passes along and close to the surface of the leadingcollecting faces of the collecting arms along a respective row as theband revolves thereby removing collected solids therefrom.

The trailing flanks of the discharging teeth are preferably circulararcs described around the centers of the roots of the discharging teethso that when in full engagement in the slots the trailing flanks of thedischarging teeth correspond to and lie along the curved surfaces of thecollecting arms.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent from the following description of a preferred embodiment takenwith reference to the accompanying drawings wherein;

FIG. 1 shows a portion of the loop conveyor band of the screening deviceaccording to the invention in front view;

FIG. 2 is a side view in section through the loop conveyor band of thescreening device shown in FIG. 1 showing a section of one continuouschain of linked collecting arms;

FIG. 3 is a perspective view of an integrally formed collecting arm andlink piece used in the loop conveyor band shown in FIG. 2;

FIG. 4 is a detailed side view of a continuous chain of linkedcollecting arms entrained around a sprocket wheel acting to drive thechain and remove collected material from the collecting arms;

FIG. 5 is a cross-sectional view of one embodiment of the cooperatingsurfaces of the discharging teeth and collecting arms of the screeningdevice according to the invention; and

FIG. 6 show side and front views of the screening device according tothe invention, in operation.

BEST MODES OF CARRYING OUT THE PRESENT INVENTION

The screening device shown in the drawings see particularly FIG. 1,comprises a continuous conveyor band of movable collecting arms 1 forscreened material arranged in parallel rows on support rods 2.

The collecting arms 1 in adjacent rows are connected together by linkpieces 3 rigidly attached at one end to a side of each collecting arm 1at the base thereof, see FIG. 3, to form endless chains of linkedcollecting arms 1 around the band.

The base of each collecting arm i is provided with a circular hole 4,see FIG. 3 for receiving the support rods 2, and the other end of thelink pieces 3 a similar circular hole 5 for receiving a support rod 2 ofthe next row of collecting arms 1 to that row carrying the collectingarms 1 to which the link pieces 3 are attached.

The free end 6 of each link piece 3 is convex, see FIG. 3, and that end7 attached to the sides of the collecting arms 1 correspondingly concaveto permit rotational clearance as between the link pieces 3 along thecontinuous chains of linked collecting arms 1.

The leading collecting faces 8 of each collecting arm 1 lie on the arcof a circle the center of which is the axis of that support rod 2 towhich the free ends of the link pieces 3 of the collecting arms 1 arerotatably attached.

As will be seen from FIG. 1, since the link pieces 3 are joined to thesides of the collecting arms 1, slots 11 are provided between the linkpieces 3 along each representative row thereof when mounted on thesupport rods 2.

The conveyor band of collecting arms 1 is revolved by means of a row ofsprocket wheels 12 mounted on a drivable shaft 12', the dischargingteeth 13 of which sprocket wheels taper to an edge 13' and mesh with theslots 11 along a representative row of collecting arms 1 as illustratedin detail in FIG. 4.

The corner portion R' of the roots R of the discharging teeth 13 isarcuate in shape to engage the corresponding arcuate shapes of the ends1' of the collecting arms, see FIG. 3, as the band is being driven bythe sprocket wheels 12. The ends 1' of the collecting arms 1 areradially described around the axis of the holes 4.

The trailing flanks 14 of the discharging teeth 13 of each sprocketwheel 12 are circular arcs the radii of which correspond to the radii ofthe circular arcs describing the faces 8 of the collecting arms 1 sothat as the sprocket wheels 12 rotate the collected material is sweptaway from leading collecting faces 8 of the collecting arms 1 by thedischarging teeth 13 as the edges 13' and flanks 14 move along in closerelationship leading collecting faces 8, and in the process clearing outmaterial trapped against the sides of the slots 11 during the screeningaction.

The advancing flanks 15 of the discharging teeth 13 are preferablychamfered to facilitate entry into the slots 11 between the link pieces3. Alternatively, the straight inwardly directed flanks of the linkpieces 3 may be locally chamfered to facilitate such entry. They arealso arcuately shaped to approximate the shape to the involute curve toa circle described about the rotational center of the sprocket wheels 12and passing through the centers of the support rods 2 or near thereto sothat stationary scrapers 16 arranged between the chains of linkedcollecting arms 1 may have a straight operational surface to cross theside or flank faces of the discharging teeth 13 at an angle of 90° orthereabouts to clear off any detritus without jamming in the manner asdisclosed in the applicant's GB Patent 2190605B.

FIG. 4 illustrates how the outer profiles of the link pieces 3, combineto form a continuous circular surface on which the scrapers 16 may ridewithout oscillation, and in the process maintain the link pieces 3 freeof any collected material.

The leading collecting surface 8 of each collecting arm 1 and thetrailing flanks 14 of the discharging teeth 13 may have male and femalematching profiles 17, 18 such as V-shapes as shown in FIG. 5. With thismodification there is much less likelihood of material finding itselfbelow the edges 15 of the discharging teeth 13 and causing an uncertainscraping action.

A screening device designed according to the invention is shown inoperational use in FIG. 6 for screening a contaminated water flowcontained in a channel 19. The conveyor band is guided at its lower endaround rotatably mounted wheels or arcuately shaped guides 20 whichengage the end caps 21 attached to the end of the support rods 2, seeFIG. 1.

An arcuately shaped stationary baffle plate 22 is positioned across thechannel 19 and of sufficient length to be close to the collecting arms 1over at least one pitch distance so that detritus is not able to passunder the transverse rows of collecting arms and avoid collection.Alternatively, in place of the baffle plate 22, a strip-brush knotshown) may be positioned across the invert of channel 19 such that thecollecting arms i pass through the strip-brush, the bristles of whichare long enough to bear onto the convex faces 3' of the link pieces 3.

The device is mounted so as to slope backwards against the direction Dof influent flow so that detritus disengaged at the top of the conveyorband may drop vertically into a transversely mounted launder channel 23without fouling the collecting arms 1.

The launder channel 23 may be sloped downwards towards one side of thedevice and continuously irregated with water or screened influent tourge collected detritus towards a collection skip (not shown) or othermeans of disposal such as apparatus for washing, de-watering andcompacting screenings, prior to bagging and disposal.

I claim:
 1. An apparatus for separating solids from liquids comprising:an endless rotatably mounted band of collecting arms (1) for collectingscreened solid material, said rotatably mounted band of collecting arms(1) further comprising a plurality of collecting arms (1), each of thecollecting arms (1) having a leading collecting face (8) and twoopposite sides adjacent said leading collecting face (8) and beingmounted on support rods (2) which are arranged in spaced relationshiparound the band; link pieces (3) rigidly attached to the collecting arms(1) for linking one support rod (2) to the next, such that the linkpieces (3) form continuous chains around the band, and separate thecollecting arms (1) one from the other to form slots (11) between thelink pieces (3), said link pieces (3) being rotatable on the supportrods (2) to which they are attached, wherein each leading collectingface (8) of each collecting arm lies on a circle, the center of which isthe axis of rotation of a support rod (2) to which a link piece (3) ofthe collecting arm (1) is attached; and a plurality of sprocket wheels(12) having a set of discharging teeth (13), said discharging teeth (13)further including a trailing flank (14) and an advancing flank (15)which taper to an edge (13') which passes along and close to the surfaceof said leading collecting faces (8) of said collecting arms (1) along arespective row as the band revolves and being arranged to cooperate withand drive said movable band by entering the slots (11) as the bandrotates to move along the leading collecting faces (8) of the collectingarms (1), thereby to remove collected material gathered at the slots(11) and from said leading collecting faces (8) of the collecting arms(1).
 2. An apparatus as claimed in claim 1 wherein the trailing flanks(14) of said discharging teeth (13) are circular arcs the radii of whichcorrespond to the radii of curvature of the leading collecting faces (8)of the collecting arms (1) so that when in full engagement in said slots(11) said trailing flanks (14) correspond to and lie along said leadingcollecting faces (8) of said collecting arms (1).
 3. An apparatus asclaimed in claim 2 wherein the leading collecting surface (8) of eachcollecting arm (1) and said trailing flanks (14) of the dischargingteeth (13) have matching profiles (17,18), which register as thetrailing flanks (14) move along the leading collecting surfaces (8) ofthe collecting arms (1).
 4. An apparatus as claimed in claim 2 whereinthe link pieces (3) have inwardly and outwardly facing edge surfaces (3,3') with respect to the endless band of which they form a part, theoutwardly facing edge surfaces (3') being arcuate so that they combineto form a continuously curved surface when moving around the sprocketwheel (12), a scraper blade (16) being mounted between adjacent ones ofsaid continuous chains to engage said arcuate surfaces (3') of the linkpieces (3) in each chain thereby to remove collected matter accumulatedthereon and from the trailing flanks (14) and advancing flanks (15) ofthe discharging teeth (13) entering the slots (11).